1. Field of the Invention
The present invention relates to a mobile radio terminal and its moving speed detecting method.
2. Description of the Related Art
In a mobile communication system to transmit a pilot signal from a base station, as a method to detect a moving speed of a mobile radio terminal, the methods such as (1) a method to estimate a speed by detecting a pitch of fading, (2) a method to estimate a speed from a time difference between a transmission frame and a reception frame, (3) a method to estimate a speed from a movement on a time axis by detecting a Path in a CDMA system and (4) a method to estimate a speed from the displacement of a career frequency by detecting a Path in a CDMA system have been already known.
The above described methods for detecting a moving speed of a mobile radio terminal had the following problems, respectively.
(1) A conventional art to estimate a speed by detecting a pitch of fading requires a lot of complicated calculations to detect a pitch and it takes much time to average the obtained pitch.
(2) According to a conventional art to estimate a speed from a time difference between a transmission frame and a reception frame, a distance between a mobile radio terminal and a base terminal is detected once to estimate a speed as its time differential. However, the distance is detected in units of 1 Chip (about 80 m in W-CDMA), so that it is not possible to detect the speed for a movement of a terminal that is shorter than the length of 1 Chip.
(3) A conventional art to estimate a speed from a movement on a time axis by detecting a Path in a CDMA system requires movement of an at least 1 Chip in order to estimate the speed as same as (2), so that it is not possible to detect the speed for a movement of a terminal that is shorter than the length of 1 Chip.
(4) According to a conventional art to estimate a speed from the displacement of a career frequency by detecting a Path in a CDMA system, generally, the number of Paths is small, namely, 2 to 6 (in W-CDMA), so that the accuracy of the estimation of the speed is low.
The present invention has been made taking the problems into consideration, an object of which is to provide a mobile radio terminal capable of detecting a moving speed of the mobile radio terminal with a time and a moving distance which are shorter compared to a conventional method and its moving speed detecting method.